Positive or Negative CASE Pressure?

[WickedWeasel]

I'm considering getting the Antec Solo case. It has a 120mm fan at the back and 2 fan mounts for 92mm fans at the lower front. If I don't install any fans in the front, then it will become a negative pressure case, and air will get sucked in from the vents in the lower front and back.

Wouldn't this cause problems for the power supply because the air may be coming in through the PS iso going out since the PS fan won't be on most of the time?

If I install 2 tricool fans at the front, then the cfm flow would be
120mm tricool fan at rear=79cfm REAR
2x 92mm tricool fans at the front=2x38=76cfm FRONT with air filter

The rear fan has a greater cfm and does not need a filter, so the case pressure would still be negative? Should I lower the fan speed at the rear to create a Positive Pressure CASE?

Does the REAR fan speed have to be greater than the HSF fan speed? HSF may be a Scythe Infinity/Ninja Plus/Shogun/Mine.

 

[Footer4321]

My rule of thumb is you want the case pressure to be higher then outside. This keeps the case from sucking air in from nearly every nook and cranny, and keeps dust levels down. I like all my air to come in through my filter, so my case stays as clean as it can. I do not think your HSF matters in this case due to it not changing the pressure in the case.

 

[zero_vertical]

assuming you have filtered intakes, you want constant positive pressure in your case, however don't overdo it. you don't want to over-rev your exhaust fans.

negative pressure will create turbulance as the air get's pulled in from multiple, unpredictable areas. you want to have control over the flow through your case to best direct the circulation where the cooling is most needed.

zv

 

[[wizard]]

so on my lanboy, i have a 120 front lower, a 120 at the rear, and a 120 blow hole on top. plus the xconnect psu pulls air out. the only place extra air can easily come in is through the drive bay slots. that would give me a negative pressure case.

this is bad?

i always assumed that as long as you can pull the air out of the case, and keep negative pressure, that you would not have hot spots as you would in positive pressure cases where air is restricted from comming out.

i thought about adding another 120 on the window, vented in towards the agp/pci slots.

 

[zero_vertical]

so on my lanboy, i have a 120 front lower, a 120 at the rear, and a 120 blow hole on top. plus the xconnect psu pulls air out. the only place extra air can easily come in is through the drive bay slots. that would give me a negative pressure case.

this is bad?

it's not the end of the world. watch your temps. longer term, you'll be attracting more dust (through non filtered penetrations) and have less "optimal" air flow. circulation in itself is most of the battle, but positive pressure is nice to help keep your componants clean and cool.

i always assumed that as long as you can pull the air out of the case, and keep negative pressure, that you would not have hot spots as you would in positive pressure cases where air is restricted from comming out..

precisely why i advise the OP not to overdo it. massive positive pressure will just create a thermal trap. i have a 120mm intake (filtered), a 120mm exhaust, and an 80mm intake (not counting psu) on my thermaltake soprano. it's a very roomy and cool case, and probably has just a tad of positive pressure, just enough to keep the ambient dust from collecting over everything inside. my old case had a lot of negative pressure (all exhaust) and my fan blades, peripheral cards, HDD, everythign were caked with dust after a few months.

on an htpc case, i'd be much more careful due to the reduced general air flow, and proximity of heat generating componants. anyone toying with a slimline case understands that a lot of tweaking and adjusting is going to be necesary with case fans.

 

[WickedWeasel]

Rear Exhaust Fan = Tricool 120mm, fan switch settings: 1=39cfm, 2=56cfm, 3=79cfm

2 x Front 92mm Tricool Fans 1=21cfm, 2=28cfm, 3=38cfm
1200rpm, 1600rpm, 2200rpm respectively

Antec Neo HE 550 PS has an 80mm fan.

To get a bit of positive pressure, set the rear to 1, and the 2 front fans to 2?
and if i overclock and need more cooling, set the rear to 2 and the front fans either to 2 and 3 or both to 3. Basically I need to experiment to find the optimal cooling efficiency, but the main objective is to maintain SOME positive pressure?

The antec Solo case has a vent at the back beside the PCI slots, do I put a piece of cardboard over it to ensure the air goes up? I won't be getting a sound card, and the video card will be a dual slot cooler like the X1900XT.

Also the power supply has a fan facing the outside of the case instead of above the HSF. The air comes from the back of the power supply. Is this a plus or minus? Should I get a differerent PS that has an internal fan that sits right above the HSF? Not sure which one is better.